The use of drilling fluids for the drilling of subterranean boreholes serves numerous purposes, including, for example, suppression of formation pressure, lubrication of the drill string, flushing drill cuttings away from the drill bit, cooling of the bottom hole assembly (BHA), and rotating turbines that provide power for various downhole tools. In general, drilling fluids are pumped down through the drill string to the tools and drill bit and circulate back to the surface via the space between the drill string and the borehole wall known as the annulus. The circulating drilling fluid carries drill cuttings, metal shavings, and other debris to the surface based. It is not uncommon for, various “foreign objects”, such as tools, rags, gravel, chunks of plastic from thread protectors, to find their way into the borehole and into the drilling fluid as well. It is desirable to remove these foreign objects and any larger particles, having a size that may damage sensitive downhole tools, such as various measurement while drilling (MWD) or logging while drilling (LWD) tools, or plug drill bit jets during the circulation process.
There are a number of different means for filtering the downhole fluid to remove unwanted particles and debris. One method employs a downhole tool that includes a filter or screen within the drill string above sensitive tools. While effective for maintaining clean drilling fluid, this type of tool generally interferes the ability to pass a wireline downhole of the tool in order to perform an explosive back-off or to retrieve radioactive sources from LWD tools in the event the drill string becomes stuck.